1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for dispensing polishing fluids in a chemical mechanical polishing system.
2. Description of the Related Art
Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits. Chemical mechanical polishing is utilized to planarize a layer of material deposited on a semiconductor wafer by moving the substrate in contact with a polishing surface while in the presence of a polishing fluid. Material is removed from the surface of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. One type of polishing fluid commonly used in chemical mechanical polishing applications is a slurry containing chemical agents and abrasive particles. The abrasive particles in the slurry enhance the mechanical removal of material from the substrate while exposing the underlying surface to the chemical agents in the polishing fluid.
Polishing fluid is typically provided to the polishing surface through a delivery arm that is positioned over the polishing surface during processing. The dispense point (i.e., the point at which the polishing fluid flows from a delivery tube to the polishing surface), and the amount and concentration of polishing fluid provided to the polishing surface are attributes that impact the quality of substrate processing. To ensure acceptable polishing results, conventional polishing fluid delivery systems rely on detent mechanisms to ensure repeatable positioning of the polishing fluid delivery arm at a pre-defined dispense location along with various flow control devices utilized to monitor and control the amount and concentration of polishing fluid delivered to the polishing surface.
One problem associated with this conventional arrangement is that the polishing fluid delivery arm is limited to the pre-defined position wherein the detent mechanism engages the arm. Thus, control of the dispense point on the polishing surface is limited to physically changing the delivery tube's position along the arm. Thus, in order to change the dispense point to achieve a desired processing result, polishing must be interrupted to allow for service personnel to mechanically adjust the position of the nozzles along the length of the slurry delivery arm, thereby increasing the risk of equipment damage and disadvantageously decreasing substrate throughput.
Another issue affecting many conventional polishing fluid delivery systems is the tendency of abrasive particles within the slurry to attach and agglomerate at tube fittings and around flow control components. For example, the interfaces between the slurry delivery tube and tees, valves, restrictors or other devices include small seams or gaps along the flow path where abrasive particles from within the slurry tend to adhere and conglomerate. As the number of abrasive particles accumulating at these locations grows, chains or groups of the conglomerated particles break free and travel downstream through the delivery tube to the polishing surface where they come in contact with the surface of the substrate being polished. These conglomerated particles often cause scratching of the substrate surface and defect generation. Therefore, it would be desirable to minimize and/or eliminate any seams along the slurry flow path to minimize the introduction of conglomerated particles to the polishing surface.
Therefore, there is a need for an improved slurry delivery system.